should i leave this on or off ??? for normal driving ?

 

Doesn't really matter, ESP is your traction control, so if you want to drag race or drive your car w/out any assistance from you car's computer, then run the ESP off, otherwise running the car w/it on helps in the snow, rain and bad conditions. You can turn the system on and off whenever you feel like while driving, it doesn't matter. It is all preference.

 

Under normal driving conditions you won't notice any difference either way. Under more extreme driving (cornering very close to the edge of being out of control) it will make a difference. By design you shouldn't be able to "feel" it when it engages. The newest version actually clears water off the brake pads when you are driving in the rain.